Means for neutralizing interference



W. H. MARTIN.

MEANS FOR NEUTRALIZING INTERFERENCE.

APPLICATION FILED FEB. 28. 1919.

1,329,842. Patented Feb. 3,1920.

2 SHEETS-SHEEI 1.

J INVENTOR.

BY WEMWZLIW/ ATTORNEY W. H. MARTIN.

MEANS FOR NEUTHALIZING INTERFERENCE.

APPLICATION FILED FEB- 28, I919- Patented Feb. 3,1920.

2 SHEETbSHEEY 2 I N V E1) TOR. WEZMMZZIZ C ATTORNEY UNITED STATES PATENT OFFICE.

WILLIAM H. MARTIN, on NEW YORK, N. Y., ASSIGNOR ro AMERICAN rnLErnoivE AND TELEGRAPH COMPANY, A GC RPORATION OF NEW YORK.

MEANS FOR N EUTRALIZING INTERFERENCE.

Specification of Letters Patent.

Patented Feb. 3, 1920.

Application filed February 25, 1919. Serial No. 279,728. 7

vented certain Improvements in Means for Neutralizing Interference, of which the following is a specification, This invention relates to signaling systerns, particularly to arrangements for the reduction of interference due to disturbing influences affecting the transmission 'line. Its'object'is to provide asimple and efficient arrangement for'the reduction or elimination of interference, especially where a numb'er of line s'are subject to the same disturb- 1 "The invention finds a most useful field in submarine cable terminals, but it is applicable also to land lines, and to complete me tallic circuits as well as to grounded lines.

,Figure 1 illustrates diagrammatically the invention applied to the reduction of interference' in a plurality of cable terminals.

" Fig. 2 shows a modification. Fig. 3 shows I another modification using no inductive connections, and Fig. 4 shows the modification of Fig. 3 applied to a set of duplexed lines.

, Referring to Fig. 1,5 and 6 represent two cables or other lines which are exposed to 30, similar disturbing'influences, such, for instance, as the inductive action of adjacent power circuits or of atmospheric disturb ances. These lines are illustrated as terminating in the usual duplex sets comprising the sending cir'cuits 7 and 8, and receiving circuits!) and 10', respectively, the receiving apparatus in each case being connected to the hue through a transformer,11 and V '12 respectively. 13 is a conductor subject to the same disturbing influences as affects I the lines 5 and 6. It may be a complete line 'paralleling the lines 5 and 6, in which'case it may, when properly balanced, be used for transmitting signals by the employing of the usual duplex arrangement provided with a sending branch 14. It may, however, be

a small gage conductor passing only through the zone of interference, and if used with cables it extends to a sea ground a suflicient distance out to intercept most of the dis turbance affecting the cables to be protected. It may be grounded through an artificial line located at the grounding point, designed with the conductor itself to simulate electrically the lines 5 and 6.

A transformer 15 has its primary in the conductor 13 for the purpose of receiving the potentials created by the disturbing'influences. Where 13 is a circuit used for sending this transformer is located 'in the receivngbranch of the duplex setas shown. 1

'lransformers 11, 12 and '15'shouldbe designed to produce similar distortion of the interference, and the impedances' connected to the secondaries ofthese "transformers Should be arrangedto permit theintcrfer-" ence voltages produced in the secondaries of the transformers to be of the same wave shape and phase. Across'theoutput'oftlie transformer 15 are connected' impeda'nces 16 and 17, and across each'impedancefis connected a vacuum tube am lifie'r,'-18and 19 respectively. The ampli ers may-have one or more stages, as the requirements-of the circuit dictate. The output circuit of the amplifier 18 is connected across the -ter-= minals of impedance 20 in the receiving circuit 9 of line 5, and the output circuit'of the amplifier 19 is connected across an impedance 21 in the receiving circuit 10 of line 6, the connection in eachcase bein so made that the voltage from the ampli er is opposed to that in the receiving-circuit due to the disturbin cause. I I

By this arrangement, it Willbeevident'that effective neutralization of the interference voltages impressed on the receiving circuit of either line may be obtained by varying the magnitude of the impedance 20'or"21,

or the amplification of the 'amplifier 18 or J '19, or by varying the amount of the -impedance'lfi or 17 across the input circuit of the amplifier. At the same time the signaling or other currents in one of the cables will have no efiect'upo'n the receiving circuit of the other cable, because vacuum tube amplifiers are unidirectional devices and permit no energy to pass back from the line toward the common connection at the controlling circuit 18. Obviously the arrangement is applicable to any number of transmission circuits which are subject to the same disturbing influences.

Fig. 2 illustrates a similar arrangement in which the connection to the several lines to be protected is inductive instead of con ductive, as in Fig. 1; also a separate transformer winding is used to supply each amplifier. The three lines 25, 26 and 27 represent a number of circuits subject to the ;Whos'e 'functions are the same as those described alt (3014119631011 with .Fig. 1.

In! 3 ,';theconnection between the corgreetingline and the amplifiers a1 and a2 iisicol dlictivci instead of. inductive as in Figs.

, and-Q. Tb provide for such .a connection -'t1i impedaa1ce,43, in the line 40 is prefereblyaso located that one or its tern'iinals is immediately connected to ground. It is helershownlas between the receiving appaiand tlhe point where the line is :fgliQilil d', buttobviously the condition is hsatisfied ifstheqianpedance 43 is in parallel with the;receivi1 rgapparatus. By then connecfii'liggthje amplifiers in parallel as shown, .the uppi'qpriate tern'iinal of each will be connected to ground. The application of the correcting voltages to the lines 46 and s7 through the iinpedances L8 and 4:9 is

si-n ilarto-tlmtin Fig. l and requires no ,ifurther explanationiexcept to note that the fin pedances 43, 48 and 49 should occupy corresponding positions in the several circuits. i-Manifestlylthe lines 40,-46and a7 may represent any sort of signaling-circuits whether (telephone, or [telegraph F-igrtshows the application of the modificationrof-Fig-fi to a ,group ot duplexed telegiraph lines v50, 51 and 52. Each line is .providedwitlr the customary ratio arms 53 and fi ticonnectetl+between the main line and the ,artificiul iline as shown, but here the tmnsmitting device preferably in series with acon'denser 56, is connected across :the :ratioaarius between the .main and artificial lines, and the receiving device 57 is confifi ted to the apex. of the ratio arms on one :side and !to ground on the other. By then mn-necting rimpedances 58, between the receiving apparatus .and .the ground in each of the lines, the interfering potentials .aris- .ing in .the ,line 50 may be applied to neuxtmli'z-ing those in the other lines and the ground connections for the amplifiers may be provided, all in the same manner as explained in connection with 3.

It ,is obvious that the circuits 5 and 6 of 1 may .be either grounded or metallic circuits, and anay .be arranged either for simple/ x or aluplex transmission, without atfectling in any Way the application of the invention here described, and the same is BEST AVAILABLE COP\ true of the circuits of Figs. 2, 3 and i. To illustrate the neutrali'zingof interference in a plurality of circuits subject to the same disturbances, two circuits only have been shown, but the application to any number of circuits is obvious, since it requires 'n'ie'rel aidu lication of the arm 'ments illustrated and described. The arrangement of impedaz'ices, 16, 17 in Fig. 1, may of course be varied in a number of obvious ways, that shown however, or any other which provides a neutral or center point, being advantageous since it allows ot a ground connection a: which is usually necessary tor amplifiers of the unbalanced type shown in Fig. 1. p

In viewof the fact that there is no appreciable time laguin the action-of the 'vaccable will be practically the same as if it were separately grounded a corresponding distance out.

Various modifications in the details, will suggest themselves to those skilled'in the art, without departing from -thecsp'irit and scope oi the invention described, and the circuit arrangements here shown are therefore .to be regarded as illustrative merely.

WVhat I claim is: I

1-. In a system for neutralizing interference, a plurality of conductors subject to the same disturbing influences, circuits interconnecting-said conductors and arranged to oppose the disturbingpotential arising in one conductor to those arising in other conductors of the group, and unidirectional devices located in said interconnecting circuits to prevent reaction between said other conductors. p

2. In a system for neutralizinginterference, ap'lurality of conductors subjectto the same disturbing influences, a neutralizing conductor also subject to thesaine influences, circuits connecting said neutralizing conductor with each-of the other conductors and arranged to oppose the disturbing potential arising in the neutralizing conductor to the disturbing potential arising in each of the other conductors, and unidirectional devices located in said connecting circuits to prevent reactions between said other conductors. 3. In a system for neutralizing ntefleronce, a plurality of conductors sub e'c't to the same disturbing influences, a neutralizing conductor also subject to the-same influences, circuits connecting said neutralizing conductor with each of the other conductors and arranged to oppose the disturbing potential arising in the neutralizing conductor to the disturbing potential arising in each of the other conductors, and unidirectional amplifying devices located in said connecting circuits to prevent reactions between said other conductors.

4. In a system for neutralizing interference, a plurality of conductors subject to the same disturbing influences a neutralizing conductor also subject to the same influences, circuits connecting said neutralizing conductor with each of the other conductors and arranged to oppose the disturbing potential arising in the neutralizing conductor to the disturbing potential arising in each of the other conductors, and vacuum tube amplitiers located in said connecting circuits to prevent reactions between said conductors.

5. In a system for neutralizing interfer-- ence, a plurality of conductors subject to the same disturbing influences, circuits interconnecting said conductors and arranged to oppose the disturbing potential arising in one conductor to those arising in other conductors of the group, and means associated with said interconnecting circuits to prevent reaction between said other conductors.

In testimony whereof I have signed m name to this specification this twenty seventh day of February, 1919.

WILLIAM H. MARTIN. 

